Dosage-dispensing devices for substances in powder- or paste form find application in particular in dispensing small quantities with high precision into small target containers. Frequently, such recipient containers are placed on a balance in order to weigh the substance delivered out of the dosage-dispensing device, so that the substance can subsequently be further processed according to given specifications.
The substance to be dispensed is contained for example in a dosage-dispensing unit which includes a source container and a dispensing head. It is desirable to deliver the substance to the outside through a small outlet opening in the dosage-dispensing device, so that the substance can be filled in a targeted stream also into a container with an opening of narrow cross-section.
Dosage-dispensing devices for dry and/or powdery substances, for example color dye powders belong to the known state of the art and are in current use. For example in U.S. Pat. No. 5,145,009 A, a dosage-dispensing device is described which includes a holder device with a receiving device and a dosage-dispensing unit. Arranged at the underside of the dosage-dispensing dispensing unit is a delivery orifice which can be opened and closed by a linear movement of a closure element. The function of the closure element is performed by a cone-shaped valve body whose diameter decreases in the upward direction. The delivery orifice is opened by lowering the vertical position of the cone-shaped valve body, which also rotates while it is in the open position and is equipped with means for advancing the substance in the direction of the delivery orifice. The dosage-dispensing unit is furthermore traversed by a drive shaft which protrudes from the top of the dosage-dispensing unit, where it is coupled to a drive source. The dosage-dispensing unit is connected at its underside to the dosage-dispensing device. The cover of the dosage-dispensing unit is functionally coupled to several pressure cylinders, through which the outlet orifice and thus the delivery rate from the dosage unit can be influenced. In dosage-dispensing devices of this kind the valve body is constrained as much as possible in a play-free manner in the dosage-dispensing unit, in order to allow the substance to be dispensed in accurate dosage quantities. Furthermore, the dispensing of doses in the microgram range involves very rigid connections between the drive source and the dosage unit that is inserted in the receiving device, because in the end phase of the dosage-dispensing process, the remaining dosage quantity is dispensed through the most minute changes of the angle of rotation and of the linear vertical position of the valve body.
The dosage-dispensing unit is set into a ring-shaped recess of the receiving device and its position is thereby defined in relation to the drive shaft and the pressure cylinders. The seating contact surface of the dosage-dispensing unit is arranged on the same plane as the delivery orifice. As the pressure cylinders apply pressure to the cover of the dosage-dispensing unit, the latter is held captive in the receiving device. In order to achieve the best seating support possible with regard to the pressure force, a large support surface is necessary. While the large diameter of the support surface and the ring-shaped constraint of the dosage-dispensing unit due to the ring-shaped recess ensure that the dosage-dispensing unit will not tip out of the ring-shaped recess as a result of asymmetric pressure forces acting on the cover, the large diameter of the support surface and the ring-shaped constraint make it difficult to achieve a compact design of the receiving device and also of the dosage-dispensing device. In this receiving device for dosage-dispensing units, substance from the dispensing process can accumulate in the ring-shaped recess between the seating surface of the dosage-dispensing unit and the receiving surface of the receiving device. A one-sided local accumulation of substance between the receiving surface and the seating surface can further lead to angular misalignment of the dosage-dispensing device relative to the receiving device, whereby the dispensing operation or the exchanging of the dosage-dispensing unit can be compromised due to distortion-causing stresses.